Placental deiodination of T4 to rT3 has been proposed as the factor controlling materno-fetal transmission of T4. We investigated T4 transfer in the isolated perfused human placental lobule with and without addition of the deiodinase inhibitor, iopanoic acid. T4 (150 nmol/L) in protein-free medium was added to the maternal circuit. Without iopanoic acid, the appearance of T4 in the fetal circuit was very low, with fetal T4 levels reaching only 4.1 +/- 0.84 pmol/L at 6 h. Levels of rT3 rose progressively in both circuits, reaching 28.8 +/- 5.5 nmol/L in the maternal and 12.4 +/- 3.2 nmol/L in the fetal circuit by 6 h. No T3 could be measured in either circuit. Addition of 0.5 nmol/L iopanoic acid to maternal perfusate, however, resulted in significant reduction in the appearance of rT3 [maternal levels, 0.58 +/- 0.06 nmol/L (2% of control values); fetal levels, 0.33 +/- 0.03 nmol/L (2.7% of control values)] and a major (approximately 2700-fold) increase in T4 appearance in the fetal circuit, with fetal T4 levels reaching 10.1 +/- 3.4 nmol/L at 6 h. These results support the hypothesis that placental inner ring (type III) deiodination is a major factor controlling placental transmission of maternal T4.

Aims The study aimed to show whether autoinduction of valproate (VPA) along its b-oxidation pathway occurred upon chronic dosing in humans.Methods Twelve young volunteers without active illness took sodium valproate (NaVPA) 200 mg orally 12 hourly for 3 weeks. On days 7 and 21, serial blood samples and all urine passed over an interdosing interval from 08.00 to 20.00 h were collected for analysis of VPA and certain metabolites. Results Plasma AUC(0,12 h) of VPA was signi®cantly lower on day 21 than on day 7 (2.40 vs 2.84 mmol ml x1 h, 95% CI for the difference 0.13±0.81 mmol ml x1 h).Signi®cant differences in plasma AUC(0,12 h) of the b-oxidation metabolites E-2-en-VPA and 3-oxo-VPA were not found. However, formation clearances of plasma VPA to urinary E-2-en-VPA and 3-oxo-VPA were signi®cantly increased from day 7 to day 21 (0.010 vs 0.024 and 2.57 vs 3.60 ml kg x1 h x1 , respectively, 95% CI for the differences x0.025 to x0.004 and x1.72 to x0.34 ml kg x1 h x1 , respectively). Formation clearances to VPA-glucuronide (0.534 vs 0.505 ml kg x1 h x1 ) and 4-OH-VPA (0.112 vs 0.110 ml kg x1 h x1 ) were not signi®cantly different. Conclusions Regular low dose VPA intake in humans over a period of 3 weeks appears to be associated with a small induction of its metabolism by the b-oxidation pathway, but not by glucuronidation or 4-hydroxylation.

Propylthiouracil (PTU) is widely believed to cross the placenta less freely than methimazole (MMI) and is therefore regarded as the preferred drug for treatment of hyperthyroidism in pregnancy. Clinical studies comparing the two drugs show, however, no differences in maternal or fetal thyroid function. We investigated transfer from the maternal to the fetal circuit in the isolated perfused term human placental lobule of low and high doses of PTU (4 micrograms/mL and 40 micrograms/mL) and MMI (1.5 micrograms/mL and 15 micrograms/mL) in protein-free perfusate and low doses of both drugs with addition of 40 g/L of bovine albumin. Both drugs readily crossed the placenta, reaching equilibrium in all experiments in about 2 h. Drug concentrations in the two circuits fitted a two compartmental model. Transfer kinetics for the two drugs were similar, nonsaturable, and unaffected by addition of albumin. Clearances (mL.min-1.g-1, means +/- SD) of PTU from maternal to fetal circuits were: 0.229 +/- 0.110, 0.216 +/- 0.065, and 0.170 +/- 0.032; and for transfer of MMI: 0.165 +/- 0.025, 0.232 +/- 0.153, and 0.174 +/- 0.009 (for low doses without, low doses with, and high doses without albumin, respectively). Clearances of PTU from fetal to maternal circuits were: 0.147 +/- 0.072, 0.109 +/- 0.014, and 0.116 +/- 0.028; and for transfer of MMI: 0.095 +/- 0.029, 0.122 +/- 0.088, and 0.12 +/- 0.005 (in the same experiments). There was no significant difference between drugs or drug doses and no effect of addition of albumin. We conclude that PTU and MMI have similar placental transfer kinetics.

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The isolated perfused lobule of human placenta was used as an in-vitro model to study the effect of intravenous immunoglobulin (IVGG) on the placental transfer of a human platelet-specific antibody (anti-P1A1). Normal human IgG was shown to transfer from the maternal to the fetal circulation of the placental model after a lag period of 2-3 h. IVGG also transferred across the placenta but only after a longer lag period (3-4 h) than normal human IgG at the same concentration, which suggests that IVGG may contain a factor that inhibits the transfer of its own component IgG. The sensitive Western immunoblotting technique was used to demonstrate progressive transfer of anti-P1A1 antibody to the fetal circulation after a 2-3 h lag period. When IVGG and anti-P1A1 antibody were added simultaneously to the maternal circulation, the transfer of platelet-specific antibody was strongly inhibited by IVGG. The inhibitory effect of IVGG on anti-P1A1 antibody transfer was consistent for three different batches of the same IVGG product (Sandoglobulin). These studies provide the first scientific data to support the use of IVGG to inhibit antiplatelet antibody transfer as part of the antenatal management of neonatal alloimmune thrombocytopenia.

1. Peripheral lobules of term placentae obtained from healthy females at Caesarian section were perfused using separate maternal and fetal circulations for 6 h periods under either oxygenated or anoxic conditions. 2. Markers of physical integrity during setting-up and initial perfusion were establishment of dual perfusion within 25 min of placental delivery, pressure in the fetal capillary network less than 40 mmHg, leakage of perfusate from fetal to maternal compartments less than or equal to 2 ml/h, and overlap of maternal with fetal perfusion as indicated visually by appropriate blanching and verified by a fetal artery to vein oxygen gradient of greater than or equal to 90 mmHg. 3. Post-perfusion markers of metabolic viability were most reliably indicated by glucose consumption (oxygenated 7.8 +/- 1.5, anoxic 17.7 +/- 1.2 mmol/kg per h), lactate production (oxygenated 8.5 +/- 1.4, anoxic 33.9 +/- 2.5 mmol/kg per h) and human placental lactogen production (oxygenated 41.2 +/- 9.8, anoxic 12.2 +/- 3.4 mg/kg per h).

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1. Plasma and urine steroid and plasma ACTH levels were measured for 2 weeks in eight subjects (six female, two male) with Cushing's disease with each given 200 mg ketoconazole orally four times daily. 2. Treatment was associated with major falls in excretion of free cortisol and the cortisol metabolites tetrahydrocortisol, 5 alpha-tetrahydrocortisol and tetrahydrocortisone. 3. Plasma cortisol and ACTH levels did not change significantly. 4. Excretion of the androgen metabolites, androsterone, 11 beta-hydroxyandrosterone and aetiocholanolone was also reduced but there was no significant fall in plasma testosterone. Plasma levels of progesterone, 17 alpha-hydroxyprogesterone and 11 beta-deoxycortisol and excretion of pregnanediol, pregnanetriol and tetrahydrodeoxycortisol rose with treatment. 5. Analysis of steroid precursor/product ratios indicated that ketoconazole significantly inhibited 11 beta-hydroxylase and 17,20-lyase but not 17 alpha-hydroxylase in these patients with Cushing's disease.